AHD technology: 720p/1080p quality via a coax at the distance of 500 m without any latency and losses
A modern market of video surveillance systems offers the widest choice of equipment and solutions, built under different technologies and tech families, such as: CCTV, HDCCTV ones. All of them differ by something, look like something else, everything has it’s own advantages and disadvantages. No wonder, it’s hard to choose the one tech, which accords to a desirable balance of sot-reliability-quality-simplicity and will meet the specific needs of a customer in so big variety of technologies.
In this article we shortly compare techs, gaining a special attention, and elaborate on AHD one.
AHD is a tech of HD/FullHD video, audio and control signal transmission via a regular coax cable at the distance of 500 m without any latencies and losses. NEXTCHIP – is the famous Korean company, developed AHD tech, whose production applies in video recorders and video cameras of the most of manufacturers of video surveillance systems.
AHD tech core features:
High image quality at the resolution of 720p/1080p
The technology uses a progressive scan while forming a signal and division of brightness and color components of an analog signal: that allows eliminating a blur and blinking, improving a color reproduction.
Reliable and inexpensive connection
AHD data transmission technology doesn’t lay a big claim on a coax cable quality. That’s why any available cable can be used for data transmission, including a composite one.
Long distance of a network laying without quality losses
Video data is transmitted without quality losses at the distance of 500 m.
AHD video camera AHD video recorder
Qualitative video without latencies
No signal latencies, indicative for IP-systems.
AHD video recorders can work in three modes, namely with three types of video cameras: standard analog D1/960H, AHD and IP ones. That allows to connect already installed IP or/and standard analog video cameras to AHD video recorder.
AHD video recorders can be easily integrated in an existing video surveillance system, in this case old analog video cameras can be replaced with AHD ones without any difficulties depending on a speed of a system modernization.
AHD video recorders support a work with Cloud service and CMS systems, providing a remote control of a system; allow to manage PTZ devices, has alarm inputs/outputs, provide an ability of a backup and has several video outputs.
It’s shown on the scheme above, how to do a remote control, adjust/maintain, get recordings from several video surveillance systems on several objects (a limitation is just by quantity of simultaneously displaying images from the same computer, i.e. you can watch no more than 64 videos from 64 video cameras at the same time), while being anywhere in the world through the Internet or Intranet, in some cases through Ethernet.
A stationary or mobile operator’s workplace is shown in “Remote control” block on the scheme. CMS system must be installed on PC, laptop or tablet PC. A video recorder address, which’s needed to get access, is specified in CMS system. Video recorders can be mounted on any territorially remote objects, which have LAN/Internet/Intranet connection.
Modernization of an existing system without extra charge
An ease of installation, fettling and maintenance. A cost of AHD equipment is comparable to a standard analog video surveillance system equipment cost.
Compatibility with any trade marks
AHD technology is opened for all manufacturers, what allows a customer to choose AHD equipment of different rival manufacturers, not worrying about its compatibility.
AHD technology elements
Basic elements of AHD tech are (an image below):
- An image processor with a signal-conditioning and AHD signal transmitting unit (ISP+AHD TX) on a video camera side;
- An audio-video codec AHD RX, forming a needed signal for a digital processor (SoC – is a system on a crystal) on a video recorder side.
The most important elements of AHD video surveillance system include:
- 1.3 or 2.0 megapixel CMOS-sensor is a part and parcel of a video camera, which transform a light flux, impinging on it’s sensitive part, into required electric signals, needed for a video image generation on a monitor or TV. It’s recommended to apply high qualitative CMOS0sensors, for example, SINY IMX 238, which have an increased sensitivity under a bad lightning (especially under IR range), for example, at night, in AHD video cameras. The most important sensor parameters are sensitivity, resolution, matrix size;
- SoC digital processor required both to receive an audio, video stream and other signals, save on a storage device and provide a convenient work of an operator of a video surveillance system under a high stability of all the system on a video recorder side;
- a video camera lens. An incorrect choice of a lens can make an image quality to become noticeably worth. So, details become blurred under a subnormal optical resolution.
A fundamental difference of AHD video cameras from standard CCTV ones is a work of ISP+AHD TX functional pair, which receives a signal from a high resolution matrix, makes a division of brightness and color components, enables to adjust a digital image processing (noise reduction. Backlight compensation, sensitivity, wide dynamic range etc.), processes PTZ-control, manage IR illumination, then transforms a digital signal into an analog one for transmission at long distances. IP video cameras differ from AHD ones by absence of a video compression, which also allows to avoid a video latency, appropriate to IP video cameras.
AHD RX audio-video codec performs the main function, which differs AHD tech from other ones, on AHD video recorder side. It can receive CVBS/COMET/AHD signals from a coax line, performing a digitalization and decoding, separation of color and brightness components, audio processing and other operations. AHD video recorder can receive audio-video and other streams from CCTV, HDCCTV, and IP video recorders in contrast to IP ones. In this case, a digital processor (SoC) processes an analog audio-video compression, but for a digital stream (from IP video cameras) SoC receives an already compressed one, as in regular IP video recorders.
Comparison table of HD-over-coax tech family and IP systems
|Resolution||700TVL||720P/1080P||720P/1080P||720P/1080P||1080P||720P/1080Р and more
|5Coax infrastructure compatibility||high||high||high||high||medium||converter is required
|6Hybrid real-time mode (CCTV+HDCCTV+IP)||no||yes||yes||yes||no||no|
|Max line distance
without repeater, m(cable 5С-2V)
cable 5С-2V, РК75-5
cable 5С-2V, РК75-5
cable 5С-2V, РК75-5
cable 5С-2V, РК75-5
cable 5С-2V, РК75-5
||coax||coax||coax||any coax||coax||twisted pair
|Cable quality requirements||medium||medium||medium||low||high||low|
||960H DVR||HDCVI DVR||HDTVI DVR||AHD DVR||SDI DVR||NVR|
1 – an open standard means, an any manufacturer can develop solutions on a base of the given technology without limits on the part of an owner of this technology;
2 – a functional pair means a type of matrix and processor applied in a video camera;
3 – a signal type specifies, what signal is transmitted over a line connecting a video camera and video recorder;
4 – a visual perception of a watching image formed by equipment of the given tech: absence of artefacts, line sharpness, saturation and other characteristics of an image;
5 – a compatibility means an ability of a successful work of equipment using already existing coax networks on an object;
6 – a capability of a video recorder to work with three types of video cameras simultaneously: standard analog, HDCCTV, IP ones;
7 – a solution difficulty means a project development one, installation and commissioning of a typical object video surveillance system;
8 – a maintenance characterizes a requirement level of skills and knowledge of an engineering personal and operators of video surveillance systems.
The comparison table shoes, that evident leaders of HDCCTV market, and probably all the market of video surveillance systems, can be three technologies: HDCVI, HDCCTV and AHD in the following years.
On the one hand, HDCVI technology compared to HDTVI and AHD is private. That poses a restriction on a technological expansion in solutions of video surveillance system manufacturers. That means, Dahua as the owner of HDCVI tech has all opportunities to provide a technical and cost leadership of its own production over other manufacturers’ solutions, to which it can sell a right to use HDCVI tech.
On the other hand, there is no difference between HDTVI and AHD technologies, but AHD one was developed by NEXTCHIP Company, whose production is applied in video recorders and video cameras of the most of manufacturers of video surveillance systems, which can be a reason of a wider expansion of AHD tech on the following years.
Accordingly, it’s reasonable to suggest that AHD tech will become the most popular on the market of video surveillance systems in the coming years.
Therefore, if a high image quality, capability of an audio record/playback and device PTZ-control at the distance of 500 m and more are requires from a video surveillance system, and a customer has a very limited budget and isn’t ready to bear with a video latency, maintenance difficulty, possible infrastructure troubles and risk of unauthorized video surveillance system access through external network nor a dependence on one manufacturer, opened AHD technology, developed by an admitted participant of the video surveillance market, absolutely is an eligible choice, to which you should pay attention first. Moreover, AHD video recorders can be an excellent solution in case of hybrid systems, including analog and IP video cameras.
AHD video recorders and AHD video cameras product line of “Proto-X” trademark is represented by three and five models accordingly.
AHD video recorders specification
|Operating system||Embedded Linux||Embedded Linux||Embedded Linux|
|Video inputs||16 BNC||8 BNC||4 BNC|
|Video outputs||1 VGA, 1 HDMI, 1 BNC||1 VGA, 1 HDMI, 1 BNC||1 VGA, 1 HDMI, 1 BNC|
|Audio inputs||2 RCA||4 RCA||4 RCA|
|Audio outputs||1 RCA||1 RCA||1 RCA|
|Monitor resolution||1920×1080, 1280×1024, 1280×720, 1024×768||1920×1080, 1280×1024, 1280×720, 1024×768||1920×1080, 1280×1024, 1280×720, 1024×768|
|Record resolution||960H / 720P / 960P||960H / 720P / 960P||960H / 720P / 960P|
|Network port||10/100 Мbit/sec, RJ45||10/100 Мbit/sec, RJ45||10/100 Мbit/sec, RJ45|
||2 × SATA HDD 4 Tb>||1 × SATA HDD 4 Tb||1 × SATA HDD 4 Tb|
|USB interface||2 × USB 2.0||2 × USB 2.0||2 × USB 2.0|
AHD video cameras specification
||Proto AHD-W13F36IR||Proto AHD-D13V212IR||Proto AHD-L13F36IR||Proto AHD-D13F36IR|
|Sensor resolution|| 1.3 Mp
|1.3 Mp (1280×960 px)||1.3 Mp
|1.3 Mp (1280×960 px)||1.3 Mp (1280×960 px)|
|Sensor + DSP|| 1/2.8" SONY IMX238 CMOS
|1/2.8" SONY IMX238 CMOS + NVP2431H||1/2.8" SONY IMX238 CMOS
|1/2.8" SONY IMX238 CMOS + NVP2431H||1/2.8" SONY IMX238 CMOS + NVP2431H|
|| 42 pcs.
||36 pcs.||30 pcs.|| 24 pcs.
|IR range|| 30 m
||30 m||30 m||20 m||25 m|
|Fixed 3,6 mm|| Varifocal
|Fixed 3,6 mm||Fixed 3,6 mm|
| Case type
Now engineers of “Proto-X” trademark are testing AHD equipment. Results of test will help to come up with the choice of a video surveillance system, and get outside of differences and nuances of modern analog technologies.